Getting unpaid rent from a Co-Signer

[Patrick Barker]

     I had a tenant who had been paying on time every month for about 8 months and then he was late, I did what you shouldn't do and gave him some extra time to get it to me... Before I know it he is MIA, unit is empty and I can't get ahold of him, however, there is a co-signer on the lease.  What is the best way to approach the co-signer to get as much of the unpaid rent as I can?

Thanks for the help!